Preparation of large-area uniform silicon nanowires arrays through metal-assisted chemical etching

A facile fabricating method has been established for large-area uniform silicon nanowires arrays. All silicon nanowires obtained were single crystals and epitaxial on the substrate. Six kinds of silicon wafers with different types, surface orientations, and doping levels were utilized as starting materials. With the catalysis of silver nanoparticles, room-temperature mild chemical etching was conducted in aqueous solution of hydrofluoric acid (HF) and hydrogen peroxide (H₂O₂). The corresponding silicon nanowires arrays with different morphologies were obtained. The silicon nanowires possess the same type and same doping level of the starting wafer. All nanowires on the substrate have the same orientation. For instance, both (100)- and (111)-oriented p-type wafers produced silicon nanowires in the (100) direction. For every kind of silicon wafer, the effect of etching conditions, such as components of etchant, temperature, and time, were systemically investigated. This is an appropriate method to produce a large amount of silicon nanowires with defined type, doping level, and growth direction for industrial applications.